Laboratory Performance Characterization of Asphalt Mixtures Containing Aging-Resistant Technologies

Abstract

Incorporating various aging-resistant technologies to prevent the adverse effects of aging into asphalt mixtures is believed to slow down the oxidative aging process of asphalt binders and, therefore, asphalt mixtures. Effective technologies would make asphalt mixtures less susceptible to fatigue cracking and extend pavement's service life. There is a necessity for the asphalt pavement industry to efficiently evaluate the effectiveness of additive technologies so that they can be implemented. The primary purpose of this study is to evaluate through laboratory testing if five anti-aging additive technologies reduce aging susceptibility and increase the cracking resistance of asphalt mixtures. The additives included (1) a thermosetting two-phase epoxy polymer and oil-based modifiers, (2) a hybrid ground tire rubber powder and a polymeric compound system, (3) a hybrid high-content polymer with pine-based chemical-based recycling agent, (4) a bio-polymer from epoxidized soybean oil, and (5) a biosynthetic, petroleum-based, and rheology modifiers blend. For this evaluation, mixtures containing two selected base binders (i.e., B1 and B5) from different sources and characteristics were modified with the additives and aged at three aging levels (i.e., Short-Term Oven Aging (STOA), Long-Term Oven Aging (LTOA), and NCAT Accelerated Weathering System(NAWS)). The effect of the additive technology on the fatigue cracking performance of the mixes after aging was evaluated through Dynamic Modulus (|E*|) and Cyclic Fatigue testing results. The Cyclic Fatigue Index (Sapp) and Glover-Rowe mix Index (G-Rm) were calculated to determine the mixtures' fatigue cracking resistance and aging susceptibility after aging. Pavement structural analysis was performed using the FlexPAVETM software to determine the percent cracking damage evolution of the mixtures for an analysis period of 20 years. Finally, the Asphalt Mixture Aging-Cracking (AMAC) model predicted 5-day oven aging at 95°C. The predicted data was compared to the experimental LTOA results for the model evaluation. The same model was also used to determine the degree of aging induced by the NAWS method in terms of days of loose mixture aging at 95°C. The results indicated that the additives effectively improved the properties related to increased cracking resistance after extended aging compared to the control mixtures. However, the effectiveness of the additive depended on the base binder and aging method.